Preparation Of Biodegradable Material Poly-?-Hydroxybutyrate

As one of the various aliphatic polyester products, poly-?- hydroxybutyrate(PHB) is most widely used among PHA products and can be produced by microbial fermentation or chemical methods. PHB is promising for biomedical applications such as human tissue repair, wound suture, pharmaceutical controlled release and so on. Besides, PHB could also be used in other areas such as biodegradable packaging materials. It could be used to substitute traditional petroleum-based general-purpose plastics, which could fundamentally reduce plastic pollution and the resulting hazards. The problems underlying the conventional microbiological synthesis are the long production cycle, high production cost and low product yield. Therefore, the main research of PHB synthesis would focus on how to reduce production cost, how to shorten the production cycle and how to improve polymer molecular weight. These three elements are also critical to the massive use of PHB.In this paper, PHB was first produced from ethyl 3-hydroxybutyrate with the method of melt condensation, and the products obtained was analyzed and characterized. In the synthetic process, in addition to the traditional heating method, microwave technology was also introduced into it. Compared to microbial synthesis, chemical synthesis could significantly shorten the response time and simplify the process, thus reducing the production cost of PHB and facilitate the massive use of PHB. Infrared(IR) analysis and Nuclear magnetic resonance(NMR) analysis were also adopted to characterize the products from experiments, and scanning electron microscopy(SEM) was used to analyze the morphology of the products, which all together contributed to the satisfactory results.When synthesizing PHB with traditional heating, ethyl 3-hydroxybutyrate was used as the raw material, and tetrabutyl titanate, the catalyst, was added to a flask containing the raw material. With a reasonable control of reaction temperature, time and other conditions, a certain molecular weight of PHB was obtained. In conventional heating, the effect of catalyst, reaction time, reaction temperature and other factors on the polymerization reaction was discussed in this paper. Among these factors, when the reaction temperature was about 160 ?, and the reaction time was 2.5h, the highest synthesizable viscosity average molecular weight of PHB could be amounted to M?=5.55?104.As to the synthesis of PHB with microwave radiation, the raw material and catalyst were added to a special flask in a microwave apparatus, with auxiliary heating medium heating the flask. The type and amount of catalyst, the microwave power and irradiation time was discussed in detail in this paper. The optimal technological conditions for this microwave method were auxiliary heating medium SiC being 40 g, microwave power 300 W and radiation time 35 min, which resulted in the highest synthesizable viscosity average molecular weight of PHB amounted to M?=13.3?104. Such molecular weight was apparently higher than that from the conventional heating, and the reaction time was just about 1/4 of the traditional method.The chemical synthesis of PHB was time saving with no need for high vacuum or inert gas shielding apparatus which was required by polymerization reaction. The method adopted in this experiment was fast, efficient, and easy to be operated, and it also proved that synthesizing PHB with chemical methods was feasible and effective.